Sulfur mustard (HD, mustard gas) is the most highly utilized chemical weapon in history, and currently it poses a serious threat to both military and civilian populations. In addition to stockpiles, HD remains one of the easiest chemical weapons to make in large quantities, and it is included in the list of likely choices for terrorist organizations. HD can be a severely debilitating agent for those exposed to it. The primary organs affected by HD are the lungs, skin and eyes. It results in acute airway edema, ARDS, bronchopneumonia, tracheobronchomalacia and/or airway stenosis, bronchiolitis obliterans, bronchiectasis, pulmonary fibrosis, asthma, and other respiratory complications. There are no specific treatments or antidotes for HD nor preventive medications to minimize its effects. Decontamination and supportive care are the only interventions recommended by current medical guidelines and more of these protect the airways. Decontamination is effective for skin and eyes only if enacted very early (< 5 minutes). Unfortunately, recognition of the problem usually does not occur within this timeframe. We hypothesize that supplementation or augmentation of airway mono- or dithiols will prevent or limit sulfur mustard toxicity. Using an animal model employing 2-chloroethyl ethyl sulfide (CEES, "half-mustard"), a less toxic analog of sulfur mustard, we will: 1) Determine airway inflammation, pro-inflammatory cytokines, and principal thiols following half-mustard aerosolization in rat, 2) evaluate effectiveness of oral and aerosolized mono- (GSH) and dithiols (lipoic acid, thioredoxin) in attenuating halfmustard lung injury (inflammation, cytokines, thiols), 3) develop novel compounds to stimulate mono- and dithiol efflux into lung epithelial lining fluid, and 4) examine the efficacy of these novel compounds in vivo. The latter studies will help us establish optimal compounds, route and mode of delivery, pharmacokinetics, bioavailability, and toxicology. Our laboratories have exceptional experience in measurement of the relevant, potentially protective thiol compounds to be evaluated. We anticipate these studies will lead to testing of the most effective compounds using authentic mustard gas at appropriate facilities.